1. Field of the Invention
The present invention relates to self-marking impact papers of the transfer or manifolding type wherein one marking ingredient is carried on one sheet of paper for reaction with a second marking ingredient normally carried on a mating sheet of paper. More particularly, the present invention relates to a dual system manifolded set of marking impact transfer or manifolding papers wherein each individual paper of the set is of a construction such that identical parts when stacked one on the other provide complete elimination of inadvertent coloration or backgrounding during handling and storage, and particularly during handling and storage of the individual sheets prior to the assemblage of the same into manifolded sets.
Impact or pressure sensitive carbonless transfer papers have recently come into wide usage in the United States and throughout the world. Ordinarily, such papers are printed and collated into manifolded sets capable of producing multiple copies. In this connection, pressure applied to the top sheet causes a corresponding mark on each of the other sheets of the set.
The top sheet of paper, upon which the impact or pressure is immediately applied, ordinarily has its back surface coated with tiny microscopic capsules containing one of the reactive ingredients which produce a mark. A receiver sheet, placed in contact with such back face of the top sheet has its front surface coated with a material having a component reactive with the contents of the capsule so that when capsules are ruptured upon impact by stylus or machine key, the contents of the ruptured capsules react with a coreactant therefor on the receiver sheet and a mark forms on the receiver sheet corresponding to the mark impressed by the stylus or machine key.
In the art, impact transfer papers are designated by the terms CB, CFB and CF, which stand respectively for "coated back," "coated front and back" and "coated front." Thus, the CB sheet is usually the top sheet and the one of which the impact impression is directly made; the CFB sheets are the intermediate sheets which form a mark on the front surface thereof and also transmit the contents of ruptured capsules from the back surface thereof to the front of the next succeeding sheet; the CF sheet is the last sheet used which is only coated on the front surface to form an image thereon and is not coated on the back surface as no further transfer is desired.
While it is customary to coat the capsules on the back surface and coat the co-reactant for the capsules on the front surface of each sheet, this procedure could be reversed if desired. Further, with some systems, coatings need not be used at all and the co-reactive ingredients may be carried in the sheets themselves, or one may be carried in one of the sheets and the other may be carried as a surface coating. Further, the reactants may both be microencapsulated liquids. Patents illustrative of the various kinds of systems that may be used in the production of manifolded transfer papers are, for example, U.S. Pat. No. 1,781,902 to Gill, U.S. Pat. No. 2,168,098 to Groak, U.S. Pat. No. 2,299,694 to Green, U.S. Pat. No. 2,348,128 to Groak, U.S. Pat. No. 2,712,507 to Green, U.S. Pat. No. 2,870,040 to Gill, Jr., U.S. Pat. No. 3,016,308 to Macaulay, and U.S. Pat. No. 3,429,827 to Ruus.
The most common variety of carbonless impact transfer paper, and the type with which this invention is primarily concerned, is the type illustrated in Green ('507) and Macaulay ('308) wherein tiny microscopic capsules containing a liqid fill comprising a chemically reactive color forming dye precursor are coated on the back surface of the sheet, and a dry coating of a co-reactant chemical for the dye precursor is coated on the front surface of a receiving sheet.
Conventionally, in the past, the practice has been to utilize a series of CFB sheets which are identical with one another in the chemical system utilized in the front coating and the back coating thereof. That is to say, the back coating of each CFB sheet is reactive with the front coating of that CFB sheet to produce a color. Thus, in a stack of CFB sheets, or in a roll of CFB paper, a front coating is always in contact with a back coating which is reactive therewith and accordingly, during handling of the stack or roll of paper, inadvertent capsule rupture may occur whereby the fill contents are transferred to the adjacent coating where discoloration of the sheet occurs. Moreover, annotation of the top sheet of a stack of such CFB papers or of the outer periphery of a roll thereof would result in the production of an image on underlying sheets.
Groak ('128) discloses a copy sheet having a coloring matter on its upper surface and a transfer coating on its lower surface which transfer coating includes a solvent in which the coloring matter is insoluble. Further, Groak discloses a second copying sheet which also has its upper surface coated with a coloring matter and has a transfer coating on its lower surface. The transfer coating of the second sheet includes a solvent in which the coloring matter of the second sheet is insoluble. Thus, with either sheet, the risk of the solvent in the transfer coating penetrating through the paper and acting on the coloring matter on the upper surface is reduced. The coloring matter of the first sheet is soluble in the solvent of the second sheet and vice versa. It is to be noted that in the Groak system, a different bottom sheet would be required depending on the total number of sheets in the entire set. Thus, if a set containing six sheets were required, the top coating on the bottom sheet must be soluble in the solvent contained in the lower surface of the fifth sheet whereas if the set includes seven sheets, the coloring matter in the coating on the upper surface of the seventh sheet must be soluble in the solvent in the transfer coating on the lower surface of the sixth sheet. Manifestly, this would require the utilization of a different bottom sheet depending on the total number of sheets in the set. It is also to be noted that the problem solved by Groak, that is penetration of one reactant through the carrier sheet to cause coloration of that same sheet, is not significant in connection with papers which include a microencapsulated reactant.